Triphenylbis(fluoroalkoxy) phosphoranes and fluorinated ketals

ABSTRACT

Novel triphenylbis(fluoroalkoxy)phosphoranes and a process for their preparation are disclosed. Also disclosed is a process for making fluorinated ketals by reacting phosphoranes with fluorinated ketones.

This is a division of application Ser. No. 08/320,624, dated Oct. 7, 1994 which is a continuation of application Ser. No. 08/029,087, filed Mar. 10, 1993, now abandoned.

Novel triphenylbis(fluoroalkoxy)phosphoranes are disclosed. Also disclosed are fluorinated ketals made from these phosphoranes with fluorinated ketones and a process for their preparation.

TECHNICAL BACKGROUND

One triphenylbis(fluoroalkoxy)phosphorane, Ph₃ P(OCH₂ CF₃)₂, has been disclosed in the literature. See the following references a-d:

a) N. Lowther and C. D. Hall, J. Chem. Soc., Chem. Comm., 1303 (1985) describe the preparation of Ar₃ P(OCH₂ CF₃)₂ (Ar=substituted phenyl rings) by the reaction of Ar_(n) P (OR)_(n-3) (n=0 to 3) with PhSOCH₂ CF₃ and the mechanisms in the hydrolysis of these phosphoranes.

b) M. Von Itzstein and I. D. Jenkins, Aust, J. Chem., 36, 557 (1983), disclose a method for the preparation of dialkoxytriphenylphosphoranes by the reaction of Ph₃ P with alcohols in the presence of azodicarboxylates and the mechanism for this reaction. This paper deals mainly with hydrocarbon phosphoranes and only one fluorinated compound Ph₃ P (OCH₂ CF₃)₂ was described. The fluorinated compound is prepared either by their new method or reaction of Ph₃ PBr₂ and CF₃ CH₂ OH in the presence of Et₃ N. The later reaction is the same as that used herein.

c) D. B. Denney et al., J. Am. Chem. Soc., 103, 1785 (1981) report the preparation of phosphoranes containing the trifluoroethoxy group and the reaction of these fluorinated phosphoranes with alkoxides such as trifluoroethoxide.

d) T. Kubota et al., J. Org. Chem., 45, 5052 (1980) used bis (2,2,2-trifluoroethoxy) triphenylphosphorane as a condensation reagent for alcohols with thiols. The preparation of Ph₃ P(OCH₂ CF₃)₂ and application of this reagent in organic synthesis is described in detail. These researchers prepared Ph₃ P (OCH₂ CF₃)₂ from the reaction of Ph₃ PBr₂ and NaOCH₂ CF₃ and investigated the reactions of Ph₃ P (OCH₂ CF₃)₂ with alcohols, carboxylic acid, thiols and amines. This reference also mentions the reaction of Ph₃ P(OCH₂ CF₃)₂ with hydrocarbon aldehydes to give the corresponding acetals.

e) Yu. G. Shermalovich et al., Zh. Org. Khim, 52, 2526 (1982) report that (CF₃)₂ C(OCH₂ CF₂ CF₂ H)₂ has been prepared from the reaction of hexafluoroacetone (HFA) and P(OCH₂ CF₂ CF₂ H)₅. The reaction of P (OCH₂ R_(f))₅ (R_(f) =((CF₂)nH, n=2,4) with carbonyl compounds is reported. Although the one mentioned fluorinated ketal, (CF₃)₂ C (CH₂ CF₂ CF₂ H)₂, was prepared by reaction of P(OCH₂ CF₂ CF₂ H)₅ with hexafluoroacetone, the starting material used was different from that used herein; applicant's starting material is Ph₃ P(OCH₂ R_(f))₂. Applicant believes that the method reported could not be adapted to prepare (CF₃)₂ (OCH₂ CF₃)₂ by the reaction of HFA with P (OCH₂ CF₃)₅.

SUMMARY OF THE INVENTION

Novel triarylbis (fluoroalkoxy) phosphoranes, 1,

    Ar.sub.3 P (OCH.sub.2 R.sub.f).sub.2                       1

are disclosed. In formula 1, Ar is phenyl (hereinafter Ph) or Ph substituted with alkyl or other substituents that are selected so as not to interfere with the process reaction. R_(f) is a perfluoroalkyl group, a perfluoroalkenyl group or a perfluoroalkynyl group of 1 to 20 carbon atoms, optionally substituted by one or more chlorine or hydrogen atoms, and optionally containing one or more oxygen atoms. The perfluoroalkyl group, perfluoroalkenyl group or perfluoroalkynyl group may be straight chain or branched, provided, however, that R_(f) is not CF₃.

Preferred R_(f) groups are selected from the group consisting of CF₂ Cl, CF₂ CF₃, CFClCF₂ Cl, and CF₂ ═CFOCF₂ CF(CF₃)OCF₂ CF₂.

Also disclosed is a process for making fluorinated ketals of the formula 2 from phosphoranes of formula 1 by reaction of these phosphoranes with fluorinated ketones. ##STR1## In formula 2: R_(f) is a perfluoroalkyl group, a perfluoroalkenyl group or a perfluoroalkynyl group of 1 to 20 carbon atoms, optionally substituted by one or more chlorine atoms, and optionally containing one or more oxygen atoms. The perfluoroalkyl group, perfluoroalkenyl group or perfluoroalkynyl group may be straight chain or branched. Preferred R_(f) groups are selected from the group consisting of CF₂ Cl, CF₂ CF₃, CFClCF₂ Cl, and CF₂ ═CFOCF₂ CF(CF₃)OCF₂ CF₂. R_(f) ' is a straight chain or branched perfluoroalkyl group, a perfluoroalkenyl group or a perfluoroalkynyl group of 1 to 20 carbon atoms, optionally substituted by one or more hydrogen atoms and optionally containing one or more oxygen atoms.

Preferred R_(f) ' groups are C₁ to C₂₀ perfluoroalkyl. Especially preferred are CF₃ and CF₂ CF₃.

The process for the preparation of various triphenylbis(fluoroalkoxy)phosphoranes involves the reaction of triphenylphosphine dibromide and the corresponding fluoroalcohols in the presence of a tertiary amine.

The triphenylbis(fluoroalkoxy)phosphorane product of this reaction can then be used to prepare fluorinated ketals when reacted with the corresponding ketones, as shown below. ##STR2## wherein R_(f) and R_(f) ' are as defined above. The process can be conducted neat or in the presence of a solvent for one or both of the reagents, within a temperature range of about 20° C. to about 250° C.

DETAILED DESCRIPTION OF THE INVENTION

Although a number of triphenylbis(alkoxy)phosphoranes, Ph₃ P(OCH₂ R)₂, have been reported in the literature, the preparation of only one triphenylbis(fluoroalkoxy) phosphorane, Ph₃ P(OCH₂ CF₃)₂, is known. The preparation of this fluorinated phosphorane was achieved by the reaction of Ph₃ P with either CF₃ CH₂ OH, in the presence of diethyl azodicarboxylate, or trifluoroethyl benzenesulfonate. Ph₃ P(OCH₂ CF₃)₂ can also be prepared by reaction of Ph₃ PBr₂ and NaOCH₂ CF₃. References for these various methods are listed in the Technical Background on page 1, herein.

An efficient process for the preparation of various triphenylbis(fluoroalkoxy)phosphoranes involves reaction of triphenylphosphine dibromide and the corresponding fluoroalcohols in the presence of a tertiary amine (e.g., triethylamine), as shown by the example, below, where R_(f) is a perfluoroalkyl group, a perfluoroalkenyl group or a perfluoroalkynyl group of 1 to 20 carbon atoms, optionally substituted by one or more chlorine or hydrogen atoms, and optionally containing one or more oxygen atoms. The perfluoroalkyl group, perfluoroalkenyl group or perfluoroalkynyl group may be straight chain or branched. Preferred R_(f) groups are selected from the group consisting of CF₂ Cl, CF₂ CF₃, CFClCF₂ Cl, and CF₂ ═CFOCF₂ CF(CF₃)OCF₂ CF₂. ##STR3## Ph₃ P(OCH₂ R_(f))₂ can then be reacted with the corresponding ketones to produce fluorinated ketals.

There appear to be no universal methods for the preparation of fiuorinated ketals of the formula (R_(f) ')₂ C (OCH₂ R_(f))₂. As indicated in the Technical Background, above, one fluorinated ketal, (CF₃)₂ C(OCH₂ CF₂ CF₂ H)₂, has been reported, which was prepared from the reaction of hexafluoroacetone (HFA) and P(OCH₂ CF₂ CF₂ H)₅. However, that reported method for making (CF₃)₂ C(OCH₂ CF₂ CF₂ H)₂ was found not to extend to prepare (CF₃)₂ C(OCH₂ CF₃)₂ by the reaction of HFA with P(OCH₂ CF₃)₅.

The present process can be carried out neat (no solvent) or in the presence of aprotic solvents such as, but not limited to, dichloromethane, 1,1,2-trifluorotrichloroethane, ether, acetonitrile, dimethylformamide (DMF), benzene, toluene and chlorobenzene.

The process is carried on at temperatures from ambient (about 20° C.) to about 250° C. A preferred temperature range is about 100° C. to about 200° C. It is most preferred to conduct the process at about 150° C. to about 200° C. There are no specific pressure requirements. Autogeneous pressure is sufficient.

The fluorinated ketals produced are useful synthetic intermediates for fluorocarbon compounds and as monomers for fluorcpolymers.

EXAMPLE 1 Synthesis of Ph₃ P(OCH₂ CF₃)₂

To a stirred solution of 136.2 g (0.52 mol) of Ph₃ P in 300 mL of of CH₂ Cl₂ was added a solution of 41.6 g (0.52 mol) of Br₂ in 100 mL of CH₂ Cl₂ at -40° C. over 1hour. After the addition was complete, the mixture was stirred at -40° C. to room temperature for 1 hour and then cooled to -40° C. A mixture of 100 g (1.0 mol) of CF₃ CH₂ OH and 101.0 g (1 mol) of Et₃ ^(N) in 400 mL of ether was added at this^(I) temperature over 1 hour and then the resulting reaction mixture was warmed to room temperature and stirred for an additional 3.5 hours. After the solids were removed by filtration under nitrogen, the filtrate was evaporated under vacuum at room temperature to give solids 209.3 g (91%). Analytic sample was obtained by slow evaporation of CH₂ Cl₂ and pentane solution. mp 138.4. ¹ H NMR (CDCl₃): 8.11-8.04 (m, 6H), 7.57-7.33 (m, 9H), 2.88 (qd, J=8.9 Hz, J=4.2 Hz, 4H); ¹⁹ F NMR (CDCl₃): -74.7 (t, J=8.9 Hz); ³¹ P NMR (CH₂ Cl₂): -58.0 (s) . Calcd. for C₂₂ H₁₉ F₆ PO₂ : C, 57.40; H, 4.16; F, 24.76; P, 6.73 Found: C, 57.27; H, 4.32; F, 24.91; P, 7.06.

EXAMPLE 2 Synthesis of Ph₃ P (OCH₂ CF₂ Cl)₂

A similar experiment using 30.0 g (0.115 mol) of Ph₃ P, 18.3 g (0.115 mol) of Br₂, 25.0 g (0.21 mol) of ClCF₂ CH₂ OH and 21.2 g (0.21 mol) of Et₃ ^(N) in 100 mL of ether and 100 mL of CH₂ Cl₂ gave 50.1 g (96.7%) of Ph₃ P(OCH₂ CF₂ Cl)₂. ¹ H NMR(CDCl₃): 8.14-8.06 (m, 6H), 7.71-7.49 (m, 9H), 3.00 (td J=11.1 Hz, J=3.8 Hz, 4H); ¹⁹ F NMR: -61.2 (t, J=11.0 Hz); ³¹ P NMR(CH₂ Cl₂): -57.7 (s). Analytic sample was obtained by slow evaporation of solution in CH₂ Cl₂ and pentane. Calcd. for C₂₂ H₁₉ F₄ Cl₂ PO₂ ; C, 53.57; H, 3.88; F, 15.41; Cl, 14.37; P, 6.28. Found: C, 53.55; H, 4.19; F, 17.39; Cl, 13.33, P, 6.84.

EXAMPLE 3 Synthesis of Ph₃ P (OCH₂ CF₂ CF₃)₂

A similar experiment using 52.4 g (0.2 mol) of Ph₃ P, 32.0 g (0.2 mol) of Br₂, 60.0 g (0.4 mol) of CF₃ CF₂ CH₂ OH and 41.8 g of Et₃ N in 150 mL of CH₂ Cl₂ and 200 mL of ether gave 105.1 g (94%) of Ph₃ P(OCH₂ CF₂ CF₃)₂. ¹ H NMR (CDCl₃): 8.07-8.01 (m, 6H), 7.54-7.33 (m, 9H), 2.95 (td, J=13.1 Hz, J=2.8 Hz, 4H); ¹⁹ F NMR (CDCl₃): -83.7 (s, 6F), -123.7 (t, J=13.2 Hz, 4F); ³¹ P NMR(CH₂ Cl₂): -57.2 (s).

EXAMPLE 4 Synthesis of Ph₃ P(OCH₂ CF₂ CF₂ H)₂

A similar experiment using 52.4 g (0.2 mol) of Ph₃ P, 32.0 g (0.2 mol) of Br₂, 54.1 g (0.41 mol) of HCF₂ CF₂ CH₂ OH and 41.4 g (0.41 mol) of Et₃ N in 250 mL of CH₂ Cl₂ and 250 mL of ether gave 96.6 g (92%) of Ph₃ P (OCH₂ CF₂ CF₂ H)₂. ¹ H NMR (CDCl₃): 8.04-9.76 (m, 4H), 7.52-7.48 (m, 9H), 5.74 (tt, J=53.4 Hz, J=5.5 Hz, 2H); ¹⁹ F NMR(CDCl₃): -126.5 (m, 4F), -141.2 (t, J=54 Hz, 4F); ³¹ P NMR(CH₂ Cl₂): -56.0 (s).

EXAMPLE 5 Synthesis of Ph₃ P (OCH₂ CFClCF₂ Cl)₂

A similar experiment using 21.0 g (0.08 mol) of Ph₃ P, 12.8 g (0.08 mol) of Br₂, 27.0 g (0.147 mol) of ClCF₂ CFClCH₂ OH and 15.0 g (0.148 mol) of Et₃ N in 100 mL of CH₂ Cl₂ and 100 mL of ether gave 38.1 g (83%) of Ph₃ P (OCH₂ CFClCF₂ Cl)₂. ¹ H NMR (CDCl₃): 8.11-8.03 (m, 6H), 7.50-7.32 (m, 9H), 3.11 (dd, J=24.6 Hz, J=3.5 Hz, 4H); ³¹ P NMR(CH₂ Cl₂): -56.4 (s).

EXAMPLE 6 Synthesis of Ph₃ P [OCH₂ (CF₂)₄ H]₂

A similar experiment using 78.6 g (0.3 mol) of Ph₃ P, 48 g (0.3 mol) of Br₂, 140.0 g (0.6 mol) of H(CF₂)₄ CH₂ OH and 61.0 g (0.6 mol) of Et₃ N in 300 mL of CH₂ Cl₂ and 300 mL of ether gave 196.7 g (90%) of Ph₃ P[OCH₂ (CF₂)₄ H]₂. ¹ H NMR(CDCl₃): 8.09-8.01 (m, 6H), 7.66-7.47 (m, 9H), 5.88 (tt, J=52.0 Hz, J=5.6 Hz, 2H), 3.02 (td, J=14.0 Hz, J=3.9 Hz); ¹⁹ F NMR: -119.7 (t, J=11.6 Hz, 4F), -125.8 (s, 4F), -131.2 (m, 4F), -138.0 (d, J=52.0 Hz, 4F); ³¹ P NMR (CH₂ Cl₂): -55.5 (s).

EXAMPLE 7 Synthesis of Ph₃ P(OCH₂ CF₂ CF₂ OCF₂ CFCF₃ OCF═CF₂)₂

A similar experiment using 22.0 g (0.084 mol) of Ph₃ P, 13.4 g (0. 084 mol) of Br₂, 59.5.0 g (0.15 mol) of CF₂ ═CFOCF₂ CF (CF₃)OCF₂ CF₂ CH₂ OH (EVEOH) and 15.2 g (0.15 mol) of Et₃ N in 100 mL of CH₂ Cl₂ and 100 mL of ether gave 59.6 g (75.3%) of Ph₃ P(OEVE)₂. ¹ H NMR(CDCl₃): 8.08-8.01 (m, 6H), 7.48-7.32 (m, 9H), 2.95 (td, J=13.7 Hz, J=4.0 Hz, 4H). ¹⁹ F NMR (CDCl₃): -80.3 (s, 6F), -83.9 (m, 4F) , -85.1 (m, 4H), -113.9 (dd, J=83.8 Hz, J=65.6 Hz, 2F), -122.1 (dd, J=112.3 Hz, J=83.8 Hz, 2F), -123.2 (t, J=13.8 Hz, 4F), -135.6 (dd, J=112.3 Hz, J=65:5 Hz, 2F), -145.4 (t, J=21.9 Hz, 2F). ³¹ p NMR (CH2Cl2): -56.2 (s).

EXAMPLE 8 Synthesis of (CF₃)₂ C (OCH₂ CF₃)₂

A solution of 420 g of Ph₃ P (OCH₂ CF₃)₂ in 300 mL of CH₂ Cl₂ was transferred into a 1L autoclave under N₂ and then pressured with 180 g of hexfluoroacetone. After being heated at 150° C. for 3 hours and 200° C. for 4 hours, the reaction mixture was poured into a flask and distilled to give the desired product 208.9 g, bp 95.5°-96° C. 99 8% purity ¹⁹ F NMR(CDCl₃): -75 1 (t, J=7.5 Hz, 6F), -76.1 (s, 6F); ¹ H NMR(CDCl₃): 4.18 (q, J=7.7 Hz) . Anal: Calcd. for C₇ H₄ F₁₂ O₂ : C, 24.15; H, 1.16; F, 65.49. Found: C, 24.21; H, 1.49; F, 65.53.

EXAMPLE 9 Synthesis of (CF₃)₂ C (OCH₂ CF₂ CF₃)₂

A mixture of 95 g of Ph₃ P (OCH₂ CF₂ CF₃)₂ and 34 g of hexafluoroacetone in 120 mL of CH₂ Cl₂ was heated in shaker tube at 150° C. for 3 hours and at 210° C. for 2 hours. Two layers were observed and the lower layer was separated and distilled to give 55.3 g of desired product (99% purity). bp 120°-121° C. ¹⁹ F NMR(CDCl₃): -76.0 (s, 6F), -84.4 (s, 6F), -124.7 (t, J=11.8 Hz, 4F); ¹ H NMR (CDCl₃): 4.22 (t, J=8.0 Hz). Anal: Calcd. for C₉ H₄ F₁₆ O₂ : C, 24.12; H, 0.90. Found: C, 24.48; H, 1.04.

EXAMPLE 10 Synthesis of (CF₃)₂ C (OCH₂ CF₂ CF₂ H)₂

A mixture of 84 g of Ph₃ P (OCH₂ CF₂ CF₂ H)₂ and 27 g of hexafluoroacetone in 100 mL of CH₂ Cl₂ was heated in shaker tube at 150° C. for 6 hours. After evaporation of the CH₂ Cl₂, the residue was distilled under partial vacuum (30 mmHg) to give 56.8 g of crude product (88% purity). Redistillation gave 36.8 g pure product (99.8% purity), bp 72° C./30 mmHg). ¹⁹ F NMR (CDCl₃): -75.9 (s, 6F), -124.7 (t, J=12.2 Hz, 4F), -138.4 (d, J=53.0 Hz, 4F); ¹ H NMR (CDCl₃): 5.92 (tt, J=53.0 Hz, J=3.8 Hz, 2H), 4.20 (t, J=12.0 Hz, 4H).

EXAMPLE 11 Synthesis of (CF₃ CF₂)₂ C (OCH₂ CF₃)₂

A mixture of 23 g of Ph₃ P(OCH₂ CF₃)₂ and 13.3 g of perfluoropentanone-3 in 30 mL of CH₂ Cl₂ was heated in shaker tube at 150° C. for 3 hours and 210° C. for 3 hours. After evaporation of the CH₂ Cl₂, the residue was distilled under partial vacuum (-30 mmHg) to give 7.2 g of crude product. Redistillation gave 6.8 g of pure product, bp 125°-128° C. ¹⁹ F NMR(CDCl₃): -74.4 (t, J=7.5 Hz, 6F), -79.0 (s, 6F), -117.2 (s, 4F), ¹ H NMR (CDCl₃): -4.27 (q, J=7.6 Hz) . Anal.: Calcd. for C₉ H₄ F₁₆ O₂ : C, 24.12; H, 0.90; F, 67.84. Found: C, 24.45; H, 0.95; F, 67.04.

EXAMPLE 12 Synthesis of (CF₃)₂ C (OCH₂ CF₂ CF₂ CF₂ CF₂ H)₂

A mixture of 74 g of Ph₃ P (OCH₂ CF₂ CF₂ CF₂ CF₂ H)₂ containing 16% H(CF₂)₄ CH₂ OH and 33.2 g of HFA in 70 mL of CH₂ Cl₂ was heated in shaker tube at 150° C. for 3 hours and 210° C. for 3 hours. After evaporation of the CH₂ Cl₂, the residue was distilled to give 28.8 g of product with 89% purity. Redistillation gave 21.0 g of pure product, bp 85° C./5 mmHg. ¹⁹ F NMR(CDCl₃): -76.0 (s, 6F), -121.1 (t, J=11.6 Hz, 4F), -125.7 (s, 4F), -130.4 (s, 4F), -137.8 (d, J=50.1 Hz, 4F). Anal: Calcd. for C₁₃ H₆ F₂₂ O₂ : C, 25.51; H, 0.99; F, 68.28. Found: C, 25.68; H, 1.05; F, 68.01.

EXAMPLE 13 Synthesis of (CF₃)₂ C(OEVE)₂

A mixture of 59.6 g of Ph₃ P(OEVE)₂, 13.0 g of HFA in 30 mL of CH₂ Cl₂ was heated in shaker tube for 6 hours. The reaction mixture was poured into a jar and the lower layer was separated and distilled under reduced pressure to give 8.5 g of (CF₃)₂ C (OEVE)₂ . bp 65°-66° C./0.3 mmHg. ¹ H NMR: 4.54 (t, J=12.4 Hz), ¹⁹ F NMR: -75.7 (s, 6F), -80.0 (f, J=7.4 Hz, 6F), -83.3 (m, 4F), -84.7 (m, 4F), -113.3 (dd, J=85.0 Hz, J=65.6 Hz, 2F), -121.8 (dd, J=111.8 Hz, J=85.0 Hz, 2H), -123.5 (t, J =12.3 Hz, 4F), -136.1 (ddt, J=111.8 Hz, J=65.5 Hz, J=5.6 Hz, 2F), -145.2 (t, J=21.9 Hz, 2F). IR (neat): 2976 (w), 1839 (m), 1342 (s), 1315 (s), 1234 (s), 1162 (s). HRMS: Calcd. for C₁₈ H₄ F₂₉ O₆ (M-CF3): 867. 1826. Found: 866.9549.

COMPARATIVE EXAMPLE 1 A. Synthesis of P (OCH₂ CF₃)₅

A 1 L three-necked flask fitted with a mechanical stirrer, a condenser and an addition funnel was charged with 62.6 g of PCl₅ and 600 mL of anhydrous ether. The mixture was cooled at -40° C. and a solution of 155 g of CF₃ CH₂ OH, 165 g of Et₃ N in 400 mL of ether was added over 1.5 hours. After the addition was complete, the resulting mixture was stirred at -40° C. to room temperature overnight. Solids were removed by filtration under nitrogen and washed with ether. After evaporation of the ether, residue was distilled to give 126.3 g of desired product, bp 81°-82° C./9 mmHg. ¹⁹ F NMR (CDCl3): -76.0 (t, J=8.3 Hz); ¹ H NMR (CDCl₃): 4.20 (qd, J=7.1 Hz, J=7.1Hz); ¹³ C NMR: 123.75 (qd, J=276.7 Hz, J=13.0 Hz), 63.38 (qd, J=36.4 Hz, J=10.8 Hz) . ³¹ P NMR: -76.3 (s).

B. Reaction of P(OCH₂ CF₃)₅ with Hexafluoroacetone

A mixture of 62.6 g of P(OCH₂ CF₃)₅ and 16.6 g of hexafluoroacetone was heated at 150° C. in shaker tube for 8 hours. No desired product was obtained and only P(OCH₂ CF₃)₅ was recovered. When the above reaction was carried out at 210° C. for 8 hours and at 250° C. for 5 hours, no reaction was observed. 

What is claimed is:
 1. A compound of the formula Ar₃ P(OCH₂ Rf)₂, wherein Ar is Ph or substituted Ph, and R_(f) is selected from straight chain or branched perfluoroalkyl, perfluoroalkenyl, perfluoroalkynyl, perfluoroalkoxy, perfluoroalkenoxy, perfluorochloroalkyl, perfluorochloroalkenyl, perfluorochloroalkynyl, perfluorochloroalkoxy, perfluorochloroalkenoxy, fluoroalkyl, fluoroalkenyl, fluoroalkynyl, fluoroalkoxy, fluoroalkenoxy, fluorochloroalkyl, fluorochloroalkenoxy, fluorochloroalkynyl, fluorochloroalkoxy, and fluorochloroalkenoxy, of 1-20 carbon atoms, provided, however, that R_(f) is not CF₃.
 2. The compound described by claim 1 wherein R_(f) is selected from CF₂ Cl, CF₂ CF₃, CFClCF₂ Cl, and CF₂ ═CFOCF₂ CF(CF₃)OCF₂ CF₂. 